U.S. patent application number 14/399009 was filed with the patent office on 2015-04-16 for formulation comprising ionic organic compounds for use in electron transport layers.
This patent application is currently assigned to MERCK PATENT GMBH. The applicant listed for this patent is Merck Patent GmbH. Invention is credited to Stephane Berny, Nicolas Blouin, Miguel Carrasco-Orozco, Toby Cull, Amy Phillips, Priti Tiwana.
Application Number | 20150105560 14/399009 |
Document ID | / |
Family ID | 48184126 |
Filed Date | 2015-04-16 |
United States Patent
Application |
20150105560 |
Kind Code |
A1 |
Berny; Stephane ; et
al. |
April 16, 2015 |
FORMULATION COMPRISING IONIC ORGANIC COMPOUNDS FOR USE IN ELECTRON
TRANSPORT LAYERS
Abstract
The invention relates to formulations comprising ionic organic
compounds for use in electron transport layers or electron
collecting layers of organic electronic (OE) devices, more
specifically in organic photovoltaic (OPV) devices, to electron
transport layers comprising or being made through the use of such
formulations, and to OE and OPV devices comprising such
formulations or electron transport layers.
Inventors: |
Berny; Stephane;
(Southampton, GB) ; Phillips; Amy; (Southampton,
GB) ; Tiwana; Priti; (Winchester, GB) ; Cull;
Toby; (Romsey, GB) ; Carrasco-Orozco; Miguel;
(Winchester, GB) ; Blouin; Nicolas; (Southampton,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Merck Patent GmbH |
Darmstadt |
|
DE |
|
|
Assignee: |
MERCK PATENT GMBH
Darmstadt
DE
|
Family ID: |
48184126 |
Appl. No.: |
14/399009 |
Filed: |
April 12, 2013 |
PCT Filed: |
April 12, 2013 |
PCT NO: |
PCT/EP2013/001078 |
371 Date: |
November 5, 2014 |
Current U.S.
Class: |
548/156 ;
252/519.2; 252/519.21; 438/82; 548/335.1; 548/427; 548/579;
564/96 |
Current CPC
Class: |
H01L 51/0072 20130101;
C08G 2261/124 20130101; C08G 2261/3223 20130101; H01L 51/0071
20130101; C08G 2261/3246 20130101; C08G 2261/364 20130101; H01L
51/005 20130101; C08K 5/50 20130101; C08K 5/36 20130101; H01L
51/0067 20130101; H01L 51/0064 20130101; Y02E 10/549 20130101; H01L
51/4253 20130101; H01L 51/5072 20130101; H01L 51/0003 20130101;
H01L 51/4273 20130101; C08G 2261/1424 20130101; C08G 2261/1426
20130101; H01G 9/2013 20130101; C08K 5/34 20130101 |
Class at
Publication: |
548/156 ;
548/427; 548/335.1; 548/579; 564/96; 252/519.2; 252/519.21;
438/82 |
International
Class: |
H01L 51/00 20060101
H01L051/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 10, 2012 |
EP |
12003723.9 |
Claims
1. A formulation comprising an organic salt, wherein the organic
salt comprises a first ionic entity and a second counterionic
entity, characterized in that the first and second entities are
small molecules, and the first entity is an organic entity,
comprising a charged organic core comprising a single charged
moiety or a plurality of charged moieties, and optionally one or
more substituents attached to the charged organic core, at least
one of said substituents comprising a charged moiety having a
charge that is opposite in sign to, or of the same sign as, the
charged moieties of the charged organic core, and the second entity
is an organic, inorganic or organometallic entity, and the net
charge of the first entity is opposite in sign to the net charge of
the second entity.
2. The formulation according to claim 1, further comprising one or
more solvents.
3. The formulation according to claim 2, wherein the solvents are
selected from water, alcohols and polar non-alcoholic organic
solvents, or combinations of the aforementioned.
4. The formulation according to claim 3, wherein the solvent is
selected from isopropanol, ethanol, a combination of water and
isopropanol, or a combination of water and ethanol.
5. The formulation according to claim 1, wherein the first entity
comprises a moiety selected from the group consisting of
imidazolium, dialkylimidazolium, trialkylimidazolium,
dialkylpyrrolidinium, mono or dialkylpyridinium, trialkylsulfonium,
carbazolium, indolium, piperidinium, morpholinium, pyrimidinium,
pyridazinium, pyrazinium, pyrazolium, pyrrolinium, pyrimidinium,
pyrazinium, thiazolium, oxazolium, triazolium, triazinium,
guanidinium, uranium, ammonium, sulfonium, phosphonium.
6. The formulation according to claim 1, wherein the second entity
comprises a halide, borate, imide, nitrate, phosphate, sulfonate,
sulfate, succinate, naphthenate, carboxylate or O-heterocyclic
moiety.
7. The formulation according to claim 1, wherein the second entity
comprises a moiety selected from the group consisting of
imidazolium, dialkylimidazolium, trialkylimidazolium,
dialkylpyrrolidinium, mono or dialkylpyridinium, trialkylsulfonium,
carbazolium, indolium, piperidinium, morpholinium, pyrimidinium,
pyridazinium, pyrazinium, pyrazolium, pyrrolinium, pyrimidinium,
pyrazinium, thiazolium, oxazolium, triazolium, triazinium,
guanidinium, uranium, ammonium, sulfonium, phosphonium, and cations
of Group 1 of the chemical table, preferably H.sup.+, Na.sup.+ or
K.sup.+.
8. The formulation according to claim 1, wherein the first entity
comprises an organic zwitterionic compound, and the second entity
comprises an organic or inorganic counterion.
9. The formulation according to claim 8, wherein the first entity
comprises a zwitterionic dye, preferably selected from a cyanine
dye, a merocyanine dye, a squarylium dye, or a polymethine dye.
10. The formulation according to claim 1, wherein the concentration
of the salt in the solvents is from 0.001 mg/ml to 30 mg/ml.
11. The formulation according to claim 1, wherein the organic salt
is a ionic liquid (IL) or a polymerisable ionic liquid (PIL).
12. The formulation according to claim 11, wherein the
concentration of the salt in the solvents is from 0.0001 to 10 vol
%.
13. A layer comprising or being made through the use of a
formulation according to claim 1.
14. The layer according to claim 13, which is an electron transport
layer (ETL) in an organic electronic device.
15. A process of preparing a layer according to claim 13,
comprising the steps of depositing the formulation on a substrate
and removing the solvents.
16. The process according to claim 15, wherein the formulation is
deposited by spin-coating or printing, preferably slot-dye coating,
inkjet printing, spraying or doctor-blading.
17. The process according to claim 15, wherein the formulation is
processed under an atmosphere of air, N.sub.2 or water
pressure.
18. The process according to claim 15, wherein the formulation is
deposited at a temperature from 10.degree. C. to 120.degree. C.,
preferably at room temperature.
19. The process according to claim 15, wherein the layer is dried
at a temperature from room temperature to 200.degree. C.,
preferably from room temperature to 60.degree. C.
20. The process according to claim 15, wherein the layer is formed
on a substrate which is selected from an electrode, an ETL, a HTL,
a BHJ, a plastic substrate, a glass substrate, a conducting layer
or a semiconducting layer, preferably selected from a BHJ in an OPV
device or a metal oxide semiconducting layer, conducting layer or
ETLs in an inverted OPV device.
21. An organic electronic device comprising a formulation according
to claim 1 as an electron transport layer (ETL).
22. A device of claim 21, which is an optical, electrooptical,
electronic, electroluminescent or photoluminescent device, or a
component of such a device, or an assembly comprising such a device
or component.
23. An optical, electrooptical, electronic, electroluminescent or
photoluminescent device, or a component thereof, or an assembly
comprising it, which comprises a formulation according claim 1.
24. The optical, electrooptical, electronic, electroluminescent or
photoluminescent device according to claim 23, which is selected
from organic field effect transistors (OFET), organic thin film
transistors (OTFT), organic light emitting diodes (OLED), organic
light emitting transistors (OLET), organic photovoltaic devices
(OPV), organic solar cells, laser diodes, Schottky diodes,
photodiodes, photoconductors, photodetectors, memristors,
transducers, optical interconnects, light-emitting electrochemical
cells, phototransistors, tunnel junctions, spin-valve devices.
25. The device according to claim 23, which is an OFET, bulk
heterojunction (BHJ) OPV device or inverted BHJ OPV device.
26. The device according to claim 25, which is a BHJ OPV device or
an inverted BHJ OPV device comprising a cathode of aluminium, gold,
silver, calcium, magnesium or barium.
27. The component according to claim 23, which is selected from
semiconductor films, charge injection layers, charge transport
layers, interlayers, planarising layers, antistatic films, polymer
electrolyte membranes (PEM), laser materials, conducting substrates
and conducting patterns.
28. The device according to claim 23, which is an assembly selected
from integrated circuits (IC), radio frequency identification
(RFID) tags or security markings or security devices containing
them, flat panel displays or backlights thereof,
electrophotographic devices, electrophotographic recording devices,
photoswitches, organic memory devices, sensor devices, biosensors
and biochips.
Description
TECHNICAL FIELD
[0001] The invention relates to formulations comprising ionic
organic compounds for use in electron transport layers or electron
collecting layers of organic electronic (OE) devices, more
specifically in organic photovoltaic (OPV) devices, to electron
transport layers comprising or being made through the use of such
formulations, and to OE and OPV devices comprising such
formulations or electron transport layers.
BACKGROUND
[0002] Interest for interfacial layers, also called buffer layers,
has considerably risen over the last few years in electronic
devices such as organic Light-Emitting Diodes (OLEDs), Organic
Photovoltaics (OPVs), and Field-Effect Transistors (OFETs). Once
integrated into solar cells, these interfacial materials, which are
by definition enclosed between the photoactive film and one of the
electrodes, lead to an improvement in the performance and lifetime
of the devices.
[0003] The process of light conversion into electricity in organic
solar cell can be explained by a sequence of steps of different
complexity; these are:
1) light absorption and exciton creation within the active layers,
usually a BHJ (bulk heterojunction) consisting of a blend of
Electron-Donating and /Electron-Accepting (D/A) organic compounds,
2) exciton migration to D/A physical interfaces followed by their
dissociation into free charge carriers, 3) free electrons (holes)
diffusion within Acceptors (Donors) domains, 4) extraction of the
electrons (holes) from the BHJ to the cathode (anode).
[0004] The last step may be aided by the presence of an interfacial
layer which comprises a material having either electron transport
or hole transport properties, and which can thus act as electron
transport layer (ETL) or hole transport layer (HTL).
[0005] Interfacial layers are thus not involved in the charge
carrier generation process itself, and can be considered as not
active part of the organic photovoltaic (OPV) device. Such
interfacial layers can act:
1) to change the electron (hole) energy barrier at the cathode
(anode) enhancing their extraction, 2) to provide selective energy
barriers helping to decrease recombination between carriers of
different signs, 3) to change the polarity of devices, 4) as a
mechanical/chemical protective layer or seed layer for the BHJ, 5)
to redistribute the incident photon flux throughout the BHJ acting
as optical spacers.
[0006] Key consideration when choosing an interfacial material to
improve device performance are their opto-electronic properties and
their processability. Requirements for interface materials include,
for example, a suitable thickness and roughness, a good coverage
and chemical interaction with underneath layers or with substrates,
a high microstructural uniformity, a high light transmission,
selective energy levels, and a high charge carrier mobility.
[0007] Various materials have been described in the literature for
use as interfacial layers, including organic and inorganic
materials. One possible classification, depending on the nature of
the materials, comprises three main types of interfacial
layers:
1) conducting layers, 2) semiconducting layers, 3) dipole
layers.
[0008] Regarding the first type, suitable materials for conducting
interfacial layers include metals such as Ag, Au, Al, Ca, Mg, Pt,
Ba, or combinations of metals, furthermore transparent conductive
oxides (TCOs) such as ITO, IrO.sub.x, AlO.sub.x, CuO.sub.x,
NiO.sub.x, HfO.sub.x, B:ZnO, Ga:ZnO, Al:ZnO or a combination of
materials and alloys thereof. Other suitable materials include
carbon derivatives such as carbon nanotubes (CNTs). Still further
suitable materials include combinations of charged polymers, such
as PEDOT:PSS, PANI:PSS, PPy:PSS for example.
[0009] Regarding the second type, suitable materials for
semiconducting interfacial layers include inorganic oxides, such as
TiO.sub.x, BaTiO.sub.x, ZnO, SnGaZnO, InGaZnO, WO.sub.x, MoO.sub.x,
VO.sub.x, ZrO.sub.x. and organic small molecules like CBP, PTCDI,
NPD, TCTA, TPDSi.sub.2, or C.sub.60 derivatives for example,
furthermore polymers such as TFB, PFN, PVK, or a combination of
such materials.
[0010] Regarding the third type, suitable materials for dipole
interfacial layers comprise neutral small-molecular weight organic
compounds made of electron-donating and electron-accepting moities
facing to each other, creating the intrinsic electric dipole, and
being chemically linked to the underneath layer with a head
group.
[0011] In organic solar cells, the choice of the interfacial layer
determines the collection efficiency of the free charge carriers,
and thus drastically impacts on device performance and electrical
stability.
[0012] However, existing conducting, semiconducting, or dipole
layers being used as Electron-Transporting Layers generally match
only few of the specific physical properties required to increase
the overall photovoltaic parameters of the devices (V.sub.OC,
J.sub.SC, and FF). Besides, their chemical interactions with
underneath or top layers such as BHJs, substrates, electrodes or
with the environment (for example oxygen or humidity) can be a
problem for the stability of devices. Finally, in moving from
research to mass production, processes and solvents must be
carefully considered to take into consideration their environmental
and economical implications. Inorganic conducting interfacial
layers, for example, enable highly efficient and stable devices
making use of the so-called inverted architecture, however, their
processability still needs to be improved in order to be compatible
with plastic substrates.
[0013] OPV devices were initially developed in the so-called
regular structure. In this structure a transparent electrode,
usually ITO, acts as anode on top of which a hole transport layer
is deposited, which is commonly made of PEDOT:PSS. A photoactive
layer is deposited on top of said hole transport layer. An
interfacial layer acting as electron transport or electronic
collecting layer is deposited on top of the photoactive layer, and
a cathode is deposited on top of the interfacial layer.
[0014] The most commonly used interfacial layer for the transport
or collection of electrons is a conducting layer of Calcium.
Generally, this layer is 5 nm to 50 nm thick and enclosed between
the photosensitive BHJ and the cathode made of Aluminum. This
material, chosen because of its very low work function (W.sub.f),
enhances the electron-ohmic contact at the cathode and mainly
improves PCE within V.sub.OC. However, the Calcium layer can
decompose with time and diffuse into the BHJ. This
counter-productive effect dramatically decreases devices
performance and lifetime. In addition to the stability issues,
Calcium deposition constitutes a considerable bottleneck for
manufacturing processes aiming at high-through put and low-cost OPV
devices. For example, Calcium cannot be printed by means of
liquid-phase formulations, but requires an expensive and time
consuming vacuum-thermal evaporation process, typically in a
separate chamber from the production line. Besides, this
fabrication process is harsh, meaning that hot evaporated metal
atoms can chemically degrade the first few nanometers of the soft
organic materials used into BHJs. Although other alternative
conducting layers made of metals as Barium or Magnesium, for
example, have been tried as alternatives, the resulting devices
could not reach the same efficiency as those made with Calcium,
because these alternative interfacial layer materials do not suit
the physical properties to the same extent as Calcium. Furthermore,
these conducting layers still suffer from stability and cost
issues.
[0015] In prior art it has also been suggested to use
semiconducting layers as ETLs in OPV devices with regular
architecture, in replacement of conducting Calcium layers. The most
common materials are based on metal oxides such as TiO.sub.x.
However, several problems are encountered with their use. For
example, their fabrication process can require an annealing step at
temperatures from 150.degree. C. to 300.degree. C. in order to
decompose organo-metallic sources (usually based on acetates
derivatives) leading to oxides. Such high temperatures can lead to
degradation of the morphology of the underlying organic BHJ, as
well as of the back substrate, especially if the back substrate is
made of organic polymers like PET or PEN. It is also possible that
the heating step has to be combined with another processing step of
UV treatment, which is expensive and detrimental for the
performances of OPV devices as well.
[0016] Dipole layers have been developed in order to overcome some
of these problems. However, when such dipole layers are made of
mineral salts such as LiF, Li.sub.2CO.sub.3, Na.sub.2CO.sub.3,
K.sub.2CO.sub.3, Cs.sub.2CO.sub.3, CsF, Cs(acac), vacuum thermal
evaporation processes are usually required. Another alternative are
dipole layers made of neutral self-assembled molecules, however,
their full integration is problematic as they generally require the
use of toxic solvents such as methanol. Besides, these compounds
need to be chemically grafted to be fully efficient, which requires
several time-consuming steps and can lead to incomplete coverage of
the underlying layer.
[0017] Dipole layers comprising conjugated polymer electrolytes
(CPEs) have also been shown to efficiently act as ETLs in regular
OPV devices replacing Calcium. Because the cores of these organic
compounds are made of semiconducting moieties (for example
fluorene, thiophene, BTZ or carbazole units), they can absorb a
small part of the incident light. This could lead to current
generation by means of a charge transfer to the acceptor material
within BHJs. Besides, the desired physical properties of these
compounds strongly depend on the orientation of their dipole.
However, due to the fact that the dipoles are located at the end of
long alkyl chains, their reorientation can easily occur and it can
also happen that the counter-ion migrates; both situations lead to
a drop in the performances of the devices. The synthesis and
purification steps of CPEs raises also several difficulties
compared to those of small molecules. Strong dewetting effects have
also been observed on layers made of CPEs, meaning that the
physical properties of the resulting layer are not homogeneous,
which can potentially act to reduce devices performances. The same
limitations in their physical properties, processing were observed
for quinacridone derivatives incorporating pendant groups as ETLs
in regular OPV devices.
[0018] Thus there is still a need for materials that are suitable
for use in interfacial layers, like ETLs, of OPV devices, which do
not have the above-mentioned drawbacks, and have improved
properties. In particular it is desired to have interfacial layer
and ETL materials which are easy to synthesize, especially by
methods suitable for mass production, show good structural
organization and film-forming properties, exhibit good electronic
properties, especially a high charge carrier mobility, a good
processibility, a high solubility in organic solvents, and high
stability in air. Especially for use in OPV cells, there is a need
for ETL materials which enable efficient charge transport from the
photoactive layer to the cathode and lead to higher cell
efficiencies, compared to materials from prior art.
[0019] It was an aim of the present invention to provide materials
for use in ETLs of OE devices, especially in OPV devices having
regular or inverted structures, which do not show the
above-mentioned drawbacks and show the desired advantageous
properties as mentioned above. Another aim of the invention was to
extend the pool of ETL materials available to the expert. Other
aims of the present invention are immediately evident to the expert
from the following detailed description.
[0020] The inventors of the present invention have found that one
or more of the above aims can be achieved by providing materials
and formulations as disclosed and claimed hereinafter. These
formulations comprise an organic salt in solution, the salt
comprising at least a first ionic entity which is a small molecule
and comprises a charged organic core having a single charge or a
plurality of charges, the salt further comprising a second
counterionic entity of opposite sign than the first entity, which
is organic, inorganic or organo-metallic, the solution further
comprising polar solvents such as water, alcohols or polar
non-alcoholic organic solvents.
[0021] The present invention more specifically relates to the
replacement of Calcium ETLs in OPV devices by using a layer
processed from a formulation comprising solvents like water,
alcohol or other polar organic solvents, or combinations thereof,
and an organic salt as defined hereinafter. The materials in
accordance with the present invention are characterized by the
nature of the salt, which is based on two individual ionic
compounds, both being small molecular weight entities and having
net opposite signs. OPV devices comprising an ETL prepared from
such materials show V.sub.OC, FF, and J.sub.SC comparable or
improved versus OPV devices with a Calcium ETL, and much higher
performance compared to OPV devices having only a cathode of
Aluminium without an ETL.
[0022] Organic charged compounds have been disclosed in prior art
for use as dipole layers. T. V. Pho et al., Adv. Funct. Mater.
2011, 21, 4338-4341 disclose negatively charged small molecules
based on quinacridone for use in ETLs of OLEDs and OPV devices.
These molecules consist of a neutral quinacridone core and one or
more negatively charged sulfonate groups attached thereto via
hexylene chains. The ETL further comprises Sodium counterions,
leading to a globally neutral mixture. An ETL layer is deposited
from a methanol solution of these compounds between a BHJ of
{PCDTBT:PC.sub.71BM} or {Si-PCDTBT:PC.sub.71BM} and an Aluminium
cathode in a regular OPV device architecture improves the electron
collection efficiency as observed by an increase in Fill Factor
(FF) values.
[0023] However, the quinacridone derivatives and formulations as
disclosed in the above document possess several drawbacks. Thus,
due to the quinacridone core the optical bandgap is rather small
(approx. 2 eV), which can reduce the incident light coming into
inverted OPV devices, if used as ETLs. Besides, they do not possess
any hole-blocking properties. Also, the use of methanol solutions
does not fit industry standards because methanol is a toxic solvent
with a very high boiling point. Moreover, the quinacridone
derivatives are processed by spin-coating, which is not compatible
with a roll-to-roll production line and leads to a waste of
material. Finally, it has been demonstrated that the increase in
PCE of devices incorporating quinacridone-based ETLs in regular
cells is due to an increase in FF only. Such ETLs thus do not
increase the V.sub.OC as compared to control devices without buffer
layer. This suggests that the dipolar character of these ETLs does
not play any role in device performance.
[0024] Charged macromolecules, like cationic or anionic polymers in
conjunction with counterions, have also been disclosed in prior art
for use in ETLs of OLEDs (see WO 2006/029226 A1, US 2010/0096656
A1, US 2009/0230362 A1, WO 2007/126929 A2) and of OPV devices (see
WO 2005/064702 A1). The core of these polymers is neutral and the
charges are located on the termination of peripherical alkyl chains
and counterions.
[0025] Zwitterionic compounds have also been disclosed in prior art
for use in ETLs. US 2010/0145062 A1 discloses zwitterionic
tetrakis(1-imidazolyl) borates comprising a central, negatively
charged boron atom, positively charged imidazolium groups and
negative counterions, for use in the ETL of a polymer light
emitting diode (PLED). Sun et al, ACS Applied Materials &
Interfaces, published in the internet in April 2012, discloses a
layer of a zwitterionic compound, comprising a cationic moiety
which is an N-heterocyclic, ammonium or phosphonium moiety, and an
anionic sulfonyl moiety attached thereto via an alkyl chain, which
is deposited on the cathode of a polymer solar cell (PSC) to
increase its work function. WO 2005/055286 A2 discloses a
zwitterionic compound comprising a cationic moiety, which is a
heterocyclic, ammonium, guanidinium or phosphonium moiety, and an
anionic sulfonyl moiety attached thereto via an alkylene spacer,
and its use in the charge carrier transport layer of Dye Sensitized
Solar Cells (DSSCs). Since the zwitterionic compounds do not have a
net charge, they do not need a counterion and are thus not
salts.
[0026] However, the above-mentioned documents do neither disclose
nor suggest compounds or formulations and their uses as claimed
hereinafter.
SUMMARY
[0027] The invention relates to a formulation comprising an organic
salt, wherein the organic salt comprises a first ionic entity and a
second counterionic entity, characterized in that [0028] both the
first and the second entity are small molecules, and [0029] the
first entity is an organic entity, comprising [0030] a charged
organic core comprising a single charged moiety or a plurality of
charged moieties, and [0031] optionally one or more substituents
attached to the charged organic core, at least one of said
substituents comprising a charged moiety having a charge that is
opposite in sign to, or of the same sign as, the charged moieties
of the charged organic core, and [0032] the second entity is an
organic, inorganic or organometallic entity, and [0033] the net
charge of the first entity is opposite in sign to the net charge of
the second entity.
[0034] Preferably the formulation further comprises one or more
solvents and the organic salt is dissolved in said solvent(s).
[0035] Preferably the solvents are selected from polar solvents,
very preferably from water, alcohols and polar non-alcoholic
organic solvents, or combinations of the aforementioned.
[0036] In another preferred embodiment the organic salt is a ionic
liquid.
[0037] The invention further relates to a layer, preferably an
electron transport layer (ETL) in an OE device, comprising or being
made through the use of a formulation as described above and
below.
[0038] The invention further relates to a process of preparing a
layer comprising the steps of depositing the formulation as
described above and below on a substrate, removing the solvents,
and optionally drying the layer at a temperature above room
temperature.
[0039] The invention further relates to the use of a formulation or
layer as described above and below in an ETL of organic electronic
devices, preferably in OPV devices having regular or inverted
structure.
[0040] The invention further relates to the use of a formulation or
an ETL as described above and below in an optical, electrooptical,
electronic, electroluminescent or photoluminescent device, or in a
component of such a device or in an assembly comprising such a
device or component.
[0041] The invention further relates to an optical, electrooptical,
electronic, electroluminescent or photoluminescent device, or a
component thereof, or an assembly comprising it, which comprises or
is made through the use of a formulation or an ETL as described
above and below.
[0042] The optical, electrooptical, electronic, electroluminescent
and photoluminescent devices include, without limitation, organic
field effect transistors (OFET), organic thin film transistors
(OTFT), organic light emitting diodes (OLED), organic light
emitting transistors (OLET), organic photovoltaic devices (OPV),
organic solar cells, laser diodes, Schottky diodes, photodiodes,
photoconductors, photodetectors, memristor, transducers, optical
interconnects, light-emitting electrochemical cells,
phototransistors, tunnel junctions, spin-valve devices.
[0043] Preferred devices are bulk heterojunction (BHJ) OPV devices
and inverted BHJ OPV devices.
[0044] The components of the above devices include, without
limitation, semiconductor films, charge injection layers, charge
transport layers, interlayers, planarising layers, antistatic
films, polymer electrolyte membranes (PEM), laser materials,
conducting substrates and conducting patterns.
[0045] The assemblies comprising such devices or components
include, without limitation, integrated circuits (IC), radio
frequency identification (RFID) tags or security markings or
security devices containing them, flat panel displays or backlights
thereof, electrophotographic devices, electrophotographic recording
devices, photoswitches, organic memory devices, sensor devices,
biosensors and biochips.
DETAILED DESCRIPTION
[0046] As used herein, the term "polymer" will be understood to
mean a molecule of high relative molecular mass, the structure of
which essentially comprises the multiple repetition of units
derived, actually or conceptually, from molecules of low relative
molecular mass (Pure Appl. Chem., 1996, 68, 2291). The term
"oligomer" will be understood to mean a molecule of intermediate
relative molecular mass, the structure of which essentially
comprises a small plurality of units derived, actually or
conceptually, from molecules of lower relative molecular mass (Pure
Appl. Chem., 1996, 68, 2291). In a preferred meaning as used herein
present invention a polymer will be understood to mean a compound
having >1, i.e. at least 2 repeat units, preferably .gtoreq.5
repeat units, and an oligomer will be understood to mean a compound
with >1 and <10, preferably <5, repeat units.
[0047] As used herein, the terms "monomer", "small molecule" and
"small molecular weight compound" are used interchangeably, and
will be understood to mean a molecule of low relative molecular
mass, as compared to a polymer or oligomer, the structure of which
does not essentially comprise the multiple repetition of structural
units.
[0048] As used herein, the terms "donor" or "donating" and
"acceptor" or "accepting" will be understood to mean an electron
donor or electron acceptor, respectively. "Electron donor" will be
understood to mean a chemical entity that donates electrons to
another compound or another group of atoms of a compound. "Electron
acceptor" will be understood to mean a chemical entity that accepts
electrons transferred to it from another compound or another group
of atoms of a compound. (see also U.S. Environmental Protection
Agency, 2009, Glossary of technical terms,
http://www.epa.gov/oust/cat/TUMGLOSS.HTM or International Union or
Pure and Applied Chemistry, Compendium of Chemical Terminology,
Gold Book).sub.--
[0049] As used herein, the term "n-type" or "n-type semiconductor"
will be understood to mean an extrinsic semiconductor in which the
conduction electron density is in excess of the mobile hole
density, and the term "p-type" or "p-type semiconductor" will be
understood to mean an extrinsic semiconductor in which mobile hole
density is in excess of the conduction electron density (see also,
J. Thewlis, Concise Dictionary of Physics, Pergamon Press, Oxford,
1973).
[0050] As used herein, the term "conjugated" will be understood to
mean a compound (for example a polymer) that contains mainly C
atoms with sp.sup.2-hybridisation (or optionally also
sp-hybridisation), and wherein these C atoms may also be replaced
by hetero atoms. In the simplest case this is for example a
compound with alternating C--C single and double (or triple) bonds,
but is also inclusive of compounds with aromatic units like for
example 1,4-phenylene. The term "mainly" in this connection will be
understood to mean that a compound with naturally (spontaneously)
occurring defects, which may lead to interruption of the
conjugation, is still regarded as a conjugated compound.
[0051] As used herein, the term "ionic liquid (IL)" means an
organic salt that usually has a melting point below 373 K. Review
articles on ionic liquids are, for example, R. Sheldon "Catalytic
reactions in ionic liquids", Chem. Commun., 2001, 2399-2407; M. J.
Earle, K. R. Seddon "Ionic liquids. Green solvent for the future",
Pure Appl. Chem., 72 (2000), 1391-1398; P. Wasserscheid, W. Keim
"lonische Flussigkeiten--neue Losungen fur die
Ubergangsmetallkatalyse" [Ionic Liquids--Novel Solutions for
Transition-Metal Catalysis], Angew. Chem., 112 (2000), 3926-3945;
T. Welton "Room temperature ionic liquids. Solvents for synthesis
and catalysis", Chem. Rev., 92 (1999), 2071-2083 or R. Hagiwara,
Ya. Ito "Room temperature ionic liquids of alkylimidazolium cations
and fluoroanions", J. Fluorine Chem., 105 (2000), 221-227.
[0052] As used herein, the term "polymerisable ionic liquid (PIL)"
means an ionic liquid with a polymerisable or crosslinkable
functional group attached to the one of the ions, preferably the
cation, via a spacer group.
[0053] As used herein, unless stated otherwise the molecular weight
is given as the number average molecular weight M.sub.n or weight
average molecular weight M.sub.W, which is determined by gel
permeation chromatography (GPC) against polystyrene standards in
eluent solvents such as tetrahydrofuran, trichloromethane (TCM,
chloroform), chlorobenzene or 1,2,4-trichloro-benzene. Unless
stated otherwise, 1,2,4-trichlorobenzene is used as solvent. The
degree of polymerization, also referred to as total number of
repeat units, n, will be understood to mean the number average
degree of polymerization given as n=M.sub.n/M.sub.U, wherein
M.sub.n is the number average molecular weight and M.sub.U is the
molecular weight of the single repeat unit, see J. M. G. Cowie,
Polymers: Chemistry & Physics of Modern Materials, Blackie,
Glasgow, 1991.
[0054] The inventors of the present invention have found that the
use of the formulations as described above and below in ETLs can
solve many of the problems encountered in prior art when using
classical ETLs in OPV devices, and thus provide significant
advantages over the materials as used in prior art. Embodiments of
the invention providing such advantages are discussed below:
[0055] The salt used in the formulation in accordance with the
present invention is made of small molecule compounds (also
referred to as "small molecular weight" or "monomeric").
Consequently its synthesis requires less synthetic steps than that
of the polymeric materials as used in prior art. The physical
properties of the salt are less dependent on variable parameters
like those of polymers, such as molecular weight, polydispersity,
purification, or characterization, for example. This leads to a
clear reduction in the cost of production and increases the
performances reliability as compared to dipole mixtures based on
conjugated polymer electrolytes. It also provides advantages over
ZnO or TiO.sub.x nanoparticles, which suffer from size or
structural variations from batch to batch.
[0056] In the formulation in accordance with the present invention,
the salt comprises two monomeric ionic entities which have opposite
net signs, and at least one of which comprises an organic charged
core.
[0057] The first entity comprises an organic charged core, which is
for example an N-heterocyclic moiety, such as pyrrolidinium,
thiazolium, oxazolium, triazolium or carbazolium, or comprise a
sulfonium, guanidinium, phosphonium or ammonium moiety.
[0058] The second entity comprises, for example, a phosphate,
borate, carboxylate or nitrate, if the first entity has a positive
net sign. The second entity can also comprise a positively charged
organic core, for example an N-heterocyclic moiety, such as
pyrrolidinium, thiazolium, oxazolium, triazolium or carbazolium, or
comprise a sulfonium, guanidinium, phosphonium or ammonium moiety,
for example.
[0059] Both the first and the second entity can also possess a
plurality of charges, distributed on the core and/or on
peripherical charged alkyl chains. Both the viscosity and the
solubility of the two entities of the salt can be tuned by changing
their number of charges. For example, ionic-terminated alkyl
chains, or zwitterionic chains can be added. Additionally, the size
of the cores of the ionic entities as well as their chemical
functionalities can be changed by simple synthetic
modifications.
[0060] Preferred N-heterocyclic moieties are selected from the
group consisting of the following structures
##STR00001## ##STR00002##
wherein the substituents R.sup.1' to R.sup.4' each, independently
of one another, denote [0061] a straight-chain or branched alkyl
having 1-20 C atoms, which optionally can be partially fluorinated,
but not in .alpha.-position to hetero-atom, and which can also
include oxygen or/and sulfur atoms in any positions in between
carbon atoms, or [0062] saturated, partially or fully unsaturated
cycloalkyl having 5-7 C atoms, which may be substituted by alkyl
groups having 1-6 C atoms, and wherein the substituents R.sup.1',
R.sup.2', R.sup.3' and/or R.sup.4' together may also form a ring
system, and, in case of reactive compounds, one or more of the
substituents R.sup.1' to R.sup.4' may also denote an alkylene
spacer group Sp, preferably having from 2 to 12 C atoms, that is
linked to a polymerisable or crosslinkable functional group.
[0063] The polymerisable or crosslinkable functional group is
preferably an acrylate, methacrylate, fluoroacrylate,
chloroacrylate, cyanoacrylate, epoxy, oxetane, vinyloxy or styryl
group.
[0064] The first entity preferably comprises a moiety selected from
the group consisting of imidazolium, dialkylimidazolium,
trialkylimidazolium, dialkylpyrrolidinium, mono or
dialkylpyridinium, trialkylsulfonium, carbazolium, indolium,
piperidinium, morpholinium, pyrimidinium, pyridazinium, pyrazinium,
pyrazolium, pyrrolinium, pyrimidinium, pyrazinium, thiazolium,
oxazolium, triazolium, triazinium, guanidinium, uranium, ammonium,
sulfonium, phosphonium.
[0065] In another preferred embodiment the first entity comprises
an organic zwitterionic compound, preferably a zwitterionic dye,
very preferably selected from a cyanine dye, a merocyanine dye, a
squarylium dye, or a polymethine dye, and the second entity
comprises an organic or inorganic counterion.
[0066] The second entity preferably comprises an organic or
inorganic moiety, very preferably a halide, borate, imide, nitrate,
phosphate, sulfonate, sulfate, succinate, naphthenate, carboxylate
or O-heterocyclic moiety.
[0067] In another preferred embodiment the second entity is
selected from the group consisting of halides, preferably chloride,
bromide or iodide, hydrogensulfate, alkylsulfates,
fluoroalkyl-phosphates, hexafluorophosphate,
bis(trifluoromethylsulfonyl)imide, formate, trifluoroacetate,
tetrafluoroborate, oxalatoborate, tetracyanoborate, dicyanamide,
tricyanomethide, thiocyanate, methanesulfonate, triflate
(trifluoromethane-sulfonate), nonaflate
(nonafluorobutane-sulfonate), tosylate (toluene-sulfonate) and
hydrogensulfate.
[0068] Very preferably the second monomeric ionic entity is
selected from the group consisting of Cl.sup.-, Br.sup.-, I.sup.-,
[HSO.sub.4].sup.-, [CH.sub.3SO.sub.4].sup.-,
[C.sub.2H.sub.5SO.sub.4].sup.-, [C.sub.4H.sub.9SO.sub.4].sup.-,
[C.sub.6H.sub.13SO.sub.4].sup.-, [C.sub.8H.sub.17SO.sub.4].sup.-,
[O.sub.5H.sub.11O.sub.2SO.sub.4].sup.-,
[(O.sub.2F.sub.5).sub.3PF.sub.3].sup.-, [PF.sub.6].sup.-,
[N(SO.sub.2CF.sub.3).sub.2].sup.-, [HCOO].sup.-,
[CF.sub.3COO].sup.-, [BF.sub.4].sup.-,
[B(C.sub.2O.sub.4).sub.2].sup.-, [B(CN).sub.4].sup.-,
[N(CN).sub.2].sup.-, [C(CN).sub.3].sup.-, [SCN].sup.-,
[CH.sub.3SO.sub.3].sup.-, [CF.sub.3SO.sub.3].sup.-,
[C.sub.4F.sub.9SO.sub.3].sup.-,
[CH.sub.3C.sub.6H.sub.4SO.sub.3].
[0069] In another preferred embodiment the second entity is
selected from the group consisting of chloride, bromide, iodide,
tetrafluoroborate, tetracyanoborate (TCB), difluoro-dicyano borate,
fluoro-tricyano borate, perfluoroalkyl-fluoro-dicyano borate,
pentafluoroethyl-fluoro-dicyano borate,
perfluoroalkyl-difluoro-cyano borate,
pentafluoroethyl-difluoro-cyano borate, perfluoroalkyl-fluoro
borate (FAB), perfluoroalkyl-alkoxy-dicyano borate, alkoxy-tricyano
borate, methoxy-tricyano borate, ethoxy-tricyano borate,
2,2,2-trifluoroethoxy-tricyano borate,
bis(2,2,2-trifluoroethoxy)-dicyano borate, tetraphenylborate (TPB),
tetrakis(3,5-bis(trifluoromethyl)phenyl)borate (TFPB),
tetrakis(4-chlorophenyl)borate, tetrakis(4-fluorophenyl)borate,
tetrakis(pentafluorophenyl)borate,
tetrakis(2,2,2-trifluoroethoxy)borate, bis(oxalato)borate,
bis(trifluoromethylsulfonyl)imide (NTF), bis(fluorosulfonyl)imide,
bis[bis(pentafluoroethyl)phosphinyl]imide (FPI),
tris(trifluoromethylsulfonyl)methide,
(fluoroalkyl)fluorophosphates,
tris(pentafluoroethyl)trifluorophosphate (FAP),
bis(pentafluoroethyl)tetrafluorophosphate,
(pentafluoroethyl)pentafluorophosphate,
tris(nona-fluorobutyl)trifluorophosphate,
bis(nonafluorobutyl)tetrafluorophosphate,
(nonafluorobutyl)pentafluorophosphate, hexafluorophosphate,
bis(fluoro-alkyl)phosphinate, bis(pentafluoroethyl)phosphinate,
bis(nonafluorobutyl)phosphinate, (fluoroalkyl)phosphonate,
(pentafluoroethyl)phosphonate, (nonafluorobutyl)phosphonate,
nonafluorobutane sulfonate (nonaflate) (NFS),
trifluoromethanesulfonate, trifluoroacetate, methanesulfonate,
butanesulfonate, butylsulfate, hexylsulfate, octylsulfate,
dicyanamide, tricyanomethide, thiocyanate, hydrogensulfate,
trifluoroacetate, tosylate, docusates: (bis(2-2-ethyl
hexyl)sulfosuccinate (AOT), naphthenates, lauryl sulphate, alkyl
benzene sulfonates (dodecyl benzene sulfonates, linear and
branched), alkyl naphthalene sulfonate, alkyl aryl ether
phosphates, alkyl ether phosphate, alkyl carboxylates: stearate,
octoates, heptanoate, wherein preferably "alkyl" is
C.sub.1-C.sub.20 alkyl, "fluoroalkyl" is fluorinated
C.sub.1-C.sub.20 alkyl, "perfluoroalkyl" is C.sub.1-C.sub.20
perfluoroalkyl, and "aryl" is optionally substituted
C.sub.5-C.sub.8-aryl, preferably benzene.
[0070] In another preferred embodiment the second entity comprises
a moiety selected from the group consisting of imidazolium,
dialkylimidazolium, trialkylimidazolium, dialkylpyrrolidinium, mono
or dialkylpyridinium, trialkylsulfonium, carbazolium, indolium
piperidinium, morpholinium, pyrimidinium, pyridazinium, pyrazinium,
pyrazolium, pyrrolinium, pyrimidinium, pyrazinium, thiazolium,
oxazolium, triazolium, triazinium, guanidinium, ammonium,
sulfonium, phosphonium, and cations of Group 1 of the chemical
table, very preferably H.sup.+, Na.sup.+ or K.sup.+.
[0071] In another preferred embodiment the organic salt is a ionic
liquid (IL) or a polymerisable ionic liquid (PIL) comprising a,
preferably only one, cation and a, preferably only one, anion. In
this preferred embodiment the cation is preferably selected from
the preferred organic cations as described for the first moiety
above, and the anion is preferably selected from the preferred
anions as described for the second moiety above.
[0072] In another preferred embodiment the IL is a PIL selected
from the N-heterocyclic moieties of the structures shown above,
wherein one or more of the substituents R.sup.1' to R.sup.4' denote
an alkylene spacer group Sp, preferably having from 2 to 12 C
atoms, that is linked to a polymerisable or crosslinkable
functional group.
[0073] In another preferred embodiment the IL or PIL comprises a
cation selected from the following formulae
##STR00003##
wherein R on each occurrence identically or differently denotes
C.sub.1-C.sub.30 alkyl, C.sub.1-C.sub.30 alkoxy, C.sub.1-C.sub.30
thiaalkyl, C.sub.2-C.sub.8 alkenyl, C.sub.2-C.sub.8 alkynyl,
C.sub.6-C.sub.12 aryl, C.sub.6-C.sub.12 cycloalkyl,
C.sub.3-C.sub.12 heterocyclyl, C.sub.3-C.sub.12 heteroaryl,
C.sub.6-C.sub.20 alkylaryl, C.sub.6-C.sub.20 alkylcycyl,
C.sub.3-C.sub.12 alkylheteroaryl, C.sub.3-C.sub.20
alkylheterocyclyl, silane, trichlorosilane, silanol,
Ph.sub.2P(O)--, Ph.sub.2P--, Me.sub.2P(O)--, Me.sub.2P--,
Ph.sub.2P(S)--, Ph.sub.3P--N--, Me.sub.3P--N--,
FSO.sub.2CF.sub.2--, CISO.sub.2(CF.sub.2).sub.n--,
HSO.sub.3(CF.sub.2).sub.n--, HCO.sub.2(CF.sub.2).sub.n--,
FSO.sub.2NHSO.sub.2(CF.sub.2).sub.n--,
CF.sub.3SO.sub.2NHSO.sub.2(CF.sub.2).sub.n--,
C.sub.nF.sub.2n+1SO.sub.2NHSO.sub.2(CF.sub.2).sub.n--,
FSO.sub.2(CF.sub.2).sub.n--, CISO.sub.2(CF.sub.2).sub.n--,
C.sub.nF.sub.2n+1SO.sub.2NH(CF.sub.2).sub.n--, --OH, --H, --F,
--Cl, --Br, --I, --CN, --NO.sub.2, --SO.sub.3H, C.sub.1-C.sub.12
hydroxy alkyl, or a polymerisable or crosslinkable group as defined
for R.sup.1' above, wherein "Ph" denotes phenyl, "Me" denotes
methyl, and n is an integer from 1 to 48, preferably from 1 to 20,
and wherein two adjacent substituents R can be linked to each other
to form a polycyclic ring system having from 5 to 20 C atoms.
[0074] In another preferred embodiment the IL or PIL comprises an
anion which selected from the group consisting of O-substituted
heterocycles, halides, borates, fluoroborates, sulfonates,
sulfates, phosphates, fluorophosphates, carboxylates, nitrates,
very preferably from C.sub.4F.sub.9SO.sub.3.sup.-,
(O.sub.2H.sub.5).sub.2PO.sub.4.sup.-, (CH.sub.3).sub.2PO.sub.4--,
CH.sub.3SO.sub.3.sup.-, C.sub.5H.sub.11O.sub.2SO.sub.4.sup.-,
O.sub.8H.sub.17SO.sub.4.sup.-, C.sub.2H.sub.5SO.sub.4.sup.-,
HSO.sub.4.sup.-, Al.sub.2Cl.sub.7.sup.-, N(CN).sub.2.sup.-,
B(CN).sub.4.sup.-, (O.sub.2F.sub.5).sub.3PF.sub.3.sup.-,
(FSO.sub.2).sub.2N.sup.-, (CF.sub.3SO.sub.2).sub.2N.sup.-,
(C.sub.2F.sub.5SO.sub.2).sub.2N.sup.-,
(CF.sub.3SO.sub.2).sub.3C.sup.-, CF.sub.3SO.sub.3.sup.-,
CF.sub.3COO.sup.-, AsF.sub.6.sup.-, CH.sub.3COO.sup.-,
(CN).sub.2N.sup.-, (CN).sub.3C.sup.-, NO.sub.3.sup.-, Cl.sup.-,
Br.sup.-, I.sup.-, PF.sub.6.sup.-, ClO.sub.4.sup.-, BF.sub.4.sup.-,
SCN.sup.-, or mixtures thereof.
[0075] Examples for especially preferred and suitable ILs are those
of the following formulae:
##STR00004##
[0076] The formulations in accordance with the present invention
further comprise a solvent or a combination of solvents. Preferably
the solvents are selected from water, alcohols, non-alcoholic polar
organic solvents, or combinations thereof.
[0077] Very preferred solvents include water, or an organic solvent
selected from methanol, isopropanol, acetic acid, acetone, ethanol,
and dimethylsulfoxide, or combinations of the aforementioned, for
example a combination of water with one or more of the
aforementioned organic solvents.
[0078] In case of ILs or PILs the solvent preferably comprises
ethanol or isopropanol. In case of other organic salts the solvent
preferably comprises a combination of water and ethanol or a
combination of water and isopropanol. Such non-toxic solvents fit
industries toxicity standards, which is a clear advantage compared
to the overall portfolio of dipole-based formulations as described
in the literature, but also as compared to semiconducting metal
oxide formulations.
[0079] These polar solvents can be combined with other solvents and
can also be used in different combinations and volumic ratios in
order to improve both the solubility of the salt and the viscosity
of the mixture at the same time. The ability of the salt to be
dissolved and processed in a lot of different solvents is caused
inter alia by its low molecular weight, which is a clear advantage
compared to CPEs.
[0080] The organic salt is preferably dissolved in the solvent(s)
at a concentration from 0.001 to 30 mg/ml, very preferably from 0.1
to 2.5 mg/ml.
[0081] In case the organic salt is an IL or PIL, it is preferably
dissolved in the solvent(s) at a concentration from 0.0001 vol % to
10 vol %, more preferably from 0.001 vol % to 2.0 vol %.
[0082] A layer can be formed from the formulation according to the
present invention by a process comprising the steps of [0083]
depositing the formulation on a substrate, [0084] removing the
solvents for example by evaporation, preferably under heat and/or
reduced pressure, and [0085] optionally drying the layer at a
temperature above room temperature.
[0086] The formulations of the present invention may be deposited
by any suitable method. Liquid coating of devices is more desirable
than vacuum deposition techniques. Solution deposition methods are
especially preferred. The formulations of the present invention
enable the use of a number of liquid coating techniques. Preferred
deposition techniques include, without limitation, dip coating,
spin coating, ink jet printing, nozzle printing, letter-press
printing, screen printing, gravure printing, doctor blade coating,
roller printing, reverse-roller printing, offset lithography
printing, dry offset lithography printing, flexographic printing,
web printing, spray coating, dip coating, curtain coating, brush
coating, slot dye coating or pad printing.
[0087] Ink-jet printing is particularly preferred when high
resolution layers and devices needs to be prepared. Selected
formulations of the present invention may be applied to
prefabricated device substrates by ink jet printing or
microdispensing. Preferably industrial piezoelectric print heads
such as but not limited to those supplied by Aprion, Hitachi-Koki,
InkJet Technology, On Target Technology, Picojet, Spectra, Trident,
Xaar may be used to apply the organic semiconductor layer to a
substrate. Additionally semi-industrial heads such as those
manufactured by Brother, Epson, Konica, Seiko Instruments Toshiba
TEC or single nozzle microdispensers such as those produced by
Microdrop and Microfab may be used.
[0088] In order to be applied by ink jet printing or
microdispensing, the compounds or polymers should be first
dissolved in a suitable solvent. Solvents must fulfil the
requirements stated above and must not have any detrimental effect
on the chosen print head.
[0089] The formulations in accordance with the present invention
are preferably processed from solution, for example by using
spin-coating or printing techniques. These printing techniques are
less expensive than the vacuum thermal evaporation processes used
for most of conducting layers.
[0090] The layer forming process is preferably carried out at a
temperature of the substrate ranging from 10.degree. C. to
120.degree. C., in case of ILs and PILs preferably from 10.degree.
C. to 120.degree. C. in case of other organic salts preferably from
10.degree. C. to 90.degree. C. The formulation can also be coated
at Room Temperature (RT), which further decreases the cost of the
production line. On the other hand this temperature range is also
high enough to activate crosslinkable chemical functions in the
moieties of PILs. For example processing the layer at 120.degree.
C. can allow the formation of a chemically crosslinked layer made
of anions (or cations) facing cations (or anions). This can lead to
reinforced dipole strength with time. This activation process of
crosslinkable functionalities can also be achieved or supported
photochemically, for example by exposure to UV light.
[0091] As underlying substrate for example a metal oxide substrate
or BHJ of an OPV device can be used. The application of the
formulation of the present invention with the salt and the solvents
does not change the morphology of underlying layers, or of the
interfaces between the different layers of the stack by an
additional annealing step either. The processing temperature can be
selected to fit the requirements of plastic substrates as well.
[0092] The inventors of the present invention also observed that
the enhancement in devices performance is mainly due to the
presence of the salt, because they did observe any improvements in
devices performances after processing only the solvents in
accordance with the present invention, as contrary to studies on
dipole reporting by means of solvent-washing effects.
[0093] The formulation can be processed in air or in an inert gas
atmosphere, for example N.sub.2. It was observed that when the
formulation is processed in air, the device performance can be
almost the same as that obtained when the formulation is processed
under N.sub.2. This is an important difference to metal oxides
layers for which physical properties are sensitive to the
environment on which they are processed. As a result, the
fabrication costs can also be decreased and performance reliability
is enhanced.
[0094] The dipole layers in accordance with the present invention
do not require any further annealing or post-deposition treatment
to improve their microstructures or to complete conversion if for
example a pre-cursor route is needed. This is contrary to
semiconducting layers based on metal oxides as used in prior art.
This does also avoid damages of underlying layers, is compatible
with plastic substrates requirements, and is a clear improvement
compared to classical dipole-based ETLs of prior art. Without
wishing to be bound to a specific theory, these advantageous
results can be explained by the low global vapour pressure of
solvents which naturally drive the formation of the ETL dipole
layer of the present invention.
[0095] The coated layer comprising the formulation according to the
present invention after solvent removal is preferably less than 50
nm thick and less than 10 nm rough, as measured by AFM. Its
morphology is observed to be uniform. Typical dewetting issues that
are usually encountered with dipole compounds can be avoided by
tuning the volumic ratio of the different solvents used in the
formulation. The homogeneity of the thin films also constitutes an
advance compared to those of semiconducting metal oxides or
classical dipole layers as used in prior art.
[0096] Another benefit of the present invention is the improved
electrical performance of devices comprising the ETL in accordance
with the present invention. An increase in both V.sub.OC and FF can
be observed, compared to reference devices having a cathode
aluminum only. This is attributed to the intrinsic physical
properties of the salt.
[0097] The use of an ETL according to the present invention
increases the electric field at the cathode of OPV devices, which
leads to an increase in V.sub.OC. The electrical strength of
dipoles is known to strongly depend on the nature of the charged
entities, especially their size and orientation. A characterizing
feature of the ETL material of the present invention is the
presence of at least one organic charged core, which allows to
extend in the electric dipole to several atoms. This effect is even
more significant when the charged core possesses a plurality of
charges, and when the counter-entity is a mirror compound of
opposite net sign. This makes a clear difference as compared to
CPEs and quinacridone derivatives of prior art, which provide
shorter-distance dipoles localised on a single atom of their
peripherical chains. It also makes a clear difference as compared
to the compounds of prior art. for example the zwitterionic
compounds as disclosed in WO 2005/055286 A1, for which steric
contributions inherent to zwitterionic compounds constraint the
delocalization of the electrical charge to some extent.
[0098] The increase in FF highlights both the fitted structuration
of the layer and the direction of the dipole.
[0099] Another benefit when using ILs or PILs is that they are
wide-bandgap materials. This intrinsic property allows their use in
both regular and inverted OPV device configuration, without any
optical contribution to the device working mode such as optical
losses, charge transfer to acceptor or donor phase. etc. This is a
clear advantage compared to the systems described in prior art for
the same purpose such as CPEs, quinacridone derivatives and dyes,
which are absorbing light in the visible or IR range and can thus
affect OPV device performance.
[0100] The formulations of the present invention are suitable for
use in/as electron transport layers of electronic,
electroluminescent or photoluminescent components or devices. In
these devices, the formulations of the present invention are
typically applied as thin layers or films.
[0101] Thus, the present invention also provides the use of the
formulation or an ETL layer comprising it in an electronic
device.
[0102] The ETL layer may be less than about 30 microns. For various
electronic device applications, the thickness may be less than
about 1 micron thick. The layer may be deposited, for example on a
part of an electronic device, by any of the aforementioned solution
coating or printing techniques.
[0103] Further preferred embodiments of the present invention are
the following: [0104] the formulation is processed by spin-coating
or other printing techniques such as slot-dye coating, inkjet
printing, spray, doctor-blade on top of a substrate, preferentially
by spin-coating or doctor-blading, [0105] the formulation is
processed under an atmosphere of air, N.sub.2 or water pressure,
preferably under an N.sub.2 atmosphere, [0106] the formulation is
processed at a temperature from 10.degree. C. to 90.degree. C.,
preferably at room temperature, [0107] the formulation is processed
at a temperature from 10.degree. C. to 120.degree. C., preferably
at room temperature, [0108] the layer formed from the formulation
is dried at a temperature from room temperature to 200.degree. C.,
preferably from room temperature to 60.degree. C., [0109] the layer
formed form the formulation is crosslinked at a temperature from
room temperature to 200.degree. C. and/or by UV exposure, [0110]
the layer formed from the formulation is integrated in a device
selected from the group consisting of an optical component, a
magnetical component, an electrical component, an optoelectronic
component, a biosensor, a photodoide, a light-emitting diode, an
optoelectronic semiconductor chip, a semi-conductor thin film, a
field-effect transistor, a polymeric photoswitch, an organic
memory, a memristor, a transducer, a photodetector, a laser
material, an optical interconnect, a light-emitting electrochemical
cell, a solar cell, a phototransistor, a liquid crystal, a tunnel
junction, a spin-valve device, a photovoltaic cell, preferably an
organic solar cell, [0111] the layer formed from the formulation is
capable of enhancing one or more of the transport of unipolar free
charge carriers, the injection efficiency of unipolar free charge
carriers, or the extraction efficiency of unipolar free charge
carriers, and is capable of decreasing the recombination
probability of unipolar free charge carriers in optoelectronic
devices such as OPV devices, OFETs and OLEDs, [0112] the layer
formed from the formulation acts as an electron-transporting layer
(ETL) in organic electronic devices, preferably in OPV devices or
organic solar cells, [0113] the layer formed from the formulation
is provided on a substrate which is selected from an electrode, an
ETL, a HTL, a BHJ, a plastic substrate, a glass substrate, a
conducting layer or a semiconducting layer, preferably selected
from a BHJ in an OPV device or a metal oxide semiconducting layer,
conducting layer or ETLs in an inverted OPV device, [0114] the OPV
device comprises a cathode of aluminium, gold, silver, calcium or
barium, [0115] the ETL leads to an improved performance, preferably
an increase of the V.sub.OC and/or FF, of an OPV device comprising
a BHJ and an aluminium electrode, compared to a control device
having no ETL between the aluminium cathode and the BHJ, [0116] the
BHJ in the OPV device comprises a polymer-fullerene mixture, and
preferably comprises a fullerene selected from PC.sub.60BM and
PC.sub.70BM, and a polymer selected from P1, P2, P3, P4 as shown in
the examples.
[0117] The formulations according to the present invention can
additionally comprise one or more further components or additives
selected for example from surface-active compounds, lubricating
agents, wetting agents, dispersing agents, hydrophobing agents,
adhesive agents, flow improvers, defoaming agents, deaerators,
diluents which may be reactive or non-reactive, auxiliaries,
colourants, dyes or pigments, sensitizers, stabilizers, binding
agents, nanoparticles or inhibitors.
[0118] The invention additionally provides an electronic device
comprising a formulation or ETL according to the present invention.
Especially preferred electronic devices are OPV devices, in
particular bulk heterojunction (BHJ) OPV devices or inverted BHJ
OPV devices.
[0119] The OPV device can for example be of any type known from the
literature (see e.g. Waldauf et al., Appl. Phys. Lett., 2006, 89,
233517).
[0120] A first preferred OPV device according to the invention
comprises the following layers (in the sequence from bottom to
top): [0121] optionally a substrate, [0122] a high work function
electrode, preferably comprising a metal oxide, like for example
ITO, serving as anode, [0123] an optional conducting polymer layer
or hole transport layer, preferably comprising an organic polymer
or polymer blend, for example of PEDOT:PSS
(poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonate), [0124]
a layer, also referred to as "active layer", comprising a p-type
and an n-type organic semiconductor, which can exist for example as
a p-type/n-type bilayer or as distinct p-type and n-type layers, or
as blend or p-type and n-type semiconductor, forming a BHJ, [0125]
an ETL layer comprising or being formed from a formulation
according to the present invention, [0126] a low work function
electrode, preferably comprising a metal like for example aluminum,
serving as cathode, [0127] wherein at least one of the electrodes,
preferably the anode, is transparent to visible light.
[0128] A second preferred OPV device according to the invention is
an inverted OPV device and comprises the following layers (in the
sequence from bottom to top): [0129] optionally a substrate, [0130]
a high work function metal or metal oxide electrode, comprising for
example ITO, serving as cathode, [0131] an ETL layer comprising or
being formed from a formulation according to the present invention,
[0132] an active layer comprising a p-type and an n-type organic
semiconductor, situated between the electrodes, which can exist for
example as a p-type/n-type bilayer or as distinct p-type and n-type
layers, or as blend or p-type and n-type semiconductor, forming a
BHJ, [0133] an optional conducting polymer layer or hole transport
layer, preferably comprising an organic polymer or polymer blend,
for example of PEDOT:PSS, [0134] an electrode comprising a high
work function metal like for example silver, serving as anode,
[0135] wherein at least one of the electrodes, preferably the
cathode, is transparent to visible light.
[0136] The photoactive layer preferably comprises a p-type
(electron donor) semiconductor and an n-type (electron acceptor)
semiconductor.
[0137] The p-type semiconductor is for example a conjugated organic
polymer.
[0138] In a preferred embodiment in accordance with the present
invention, the p-type semiconductor is selected from conjugated
polymers or copolymers that encompass one or more repeating units
selected from thiophene-2,5-diyl, 3-substituted thiophene-2,5-diyl,
optionally substituted thieno[2,3-b]thiophene-2,5-diyl, optionally
substituted thieno[3,2-b]thiophene-2,5-diyl, selenophene-2,5-diyl,
or 3-substituted selenophene-2,5-diyl.
[0139] Further preferred p-type semiconductors are selected from
copolymers comprising electron acceptor and electron donor units.
Preferred copolymers of this preferred embodiment are for example
copolymers comprising one or more
benzo[1,2-b:4,5-b']dithiophene-2,5-diyl units that are preferably
4,8-disubstituted by one or more groups R as defined above, and
further comprising one or more aryl or heteroaryl units selected
from Group A and Group B, preferably comprising at least one unit
of Group A and at least one unit of Group B, wherein Group A
consists of aryl or heteroaryl groups having electron donor
properties and Group B consists of aryl or heteroaryl groups having
electron acceptor properties, and preferably
[0140] Group A consists of selenophene-2,5-diyl,
thiophene-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl,
thieno[2,3-b]thiophene-2,5-diyl,
selenopheno[3,2-b]selenophene-2,5-diyl,
selenopheno[2,3-b]selenophene-2,5-diyl,
selenopheno[3,2-b]thiophene-2,5-diyl,
selenopheno[2,3-b]thiophene-2,5-diyl,
benzo[1,2-b:4,5-b']dithiophene-2,6-diyl, 2,2-dithiophene,
2,2-diselenophene, dithieno[3,2-b:2',3'-d]silole-5,5-diyl,
4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl,
2,7-di-thien-2-yl-carbazole, 2,7-di-thien-2-yl-fluorene,
indaceno[1,2-b:5,6-b']dithiophene-2,7-diyl,
benzo[1'',2'':4,5;4'',5'':4',5']bis(silolo[3,2-b:3',2'-b']thiophene)-2,7--
diyl, 2,7-di-thien-2-yl-indaceno[1,2-b:5,6-b']dithiophene,
2,7-di-thien-2-yl-benzo[1'',2'':4,5;4'',5'':4',5']bis(silolo[3,2-b:3',2'--
b']thiophene)-2,7-diyl, and
2,7-di-thien-2-yl-phenanthro[1,10,9,8-c,d,e,f,g]carbazole, all of
which are optionally substituted by one or more, preferably one or
two groups R, and
[0141] Group B consists of benzo[2,1,3]thiadiazole-4,7-diyl,
5,6-dialkyl-benzo[2,1,3]thiadiazole-4,7-diyl,
5,6-dialkoxybenzo[2,1,3]thiadiazole-4,7-diyl,
benzo[2,1,3]selenadiazole-4,7-diyl,
5,6-dialkoxy-benzo[2,1,3]selenadiazole-4,7-diyl,
benzo[1,2,5]thiadiazole-4,7,diyl,
benzo[1,2,5]selenadiazole-4,7,diyl,
benzo[2,1,3]oxadiazole-4,7-diyl,
5,6-dialkoxybenzo[2,1,3]oxadiazole-4,7-diyl,
2H-benzotriazole-4,7-diyl, 2,3-dicyano-1,4-phenylene, 2,5-dicyano,
1,4-phenylene, 2,3-difluoro-1,4-phenylene,
2,5-difluoro-1,4-phenylene, 2,3,5,6-tetrafluoro-1,4-phenylene,
3,4-difluorothiophene-2,5-diyl, thieno[3,4-b]pyrazine-2,5-diyl,
quinoxaline-5,8-diyl, thieno[3,4-b]thiophene-4,6-diyl,
thieno[3,4-b]thiophene-6,4-diyl, and
3,6-pyrrolo[3,4-c]pyrrole-1,4-dione, all of which are optionally
substituted by one or more, preferably one or two groups R,
wherein R is H, F, Cl or alkyl, alkoxy, thioalkyl, fluoroalkyl,
carbonylalkyl, carbonyloxaalkyl, oxacarbonylalkyl, aryl,
heteroaryl, aryloxy or heteroaryloxy with 1 to 30 C atoms, wherein
the aryl and heteroaryl groups may also be substituted by fluoro,
alkyl or alkoxy groups.
[0142] The n-type semiconductor can be an inorganic material such
as zinc oxide (ZnO.sub.x), zinc tin oxide (ZTO), titanium oxide
(TiO.sub.x), molybdenum oxide (MoO.sub.x), nickel oxide
(NiO.sub.x), or cadmium selenide (CdSe), or an organic material
such as graphene or a fullerene or substituted fullerene, for
example an indene-C.sub.60-fullerene bisaduct like ICBA, or a
(6,6)-phenyl-butyric acid methyl ester derivatized methano C.sub.60
fullerene, also known as "PCBM-C.sub.60" or "C.sub.60PCBM", as
disclosed for example in G. Yu, J. Gao, J. C. Hummelen, F. Wudl, A.
J. Heeger, Science 1995, Vol. 270, p. 1789 ff and having the
structure shown below, or structural analogous compounds with e.g.
a C.sub.61 fullerene group, a C.sub.70 fullerene group, or a
O.sub.71 fullerene group, or an organic polymer (see for example
Coakley, K. M. and McGehee, M. D. Chem. Mater. 2004, 16, 4533).
##STR00005##
[0143] Preferably the p-type semiconductor is blended with an
n-type semiconductor such as a fullerene or substituted fullerene,
like for example PCBM-C.sub.60, PCBM-C.sub.70, PCBM-C.sub.61,
PCBM-C.sub.71, bis-PCBM-C.sub.61, bis-PCBM-C.sub.71, ICBA
(1',1'',4',4''-tetrahydro-di[1,4]methanonaphthaleno[1,2:2',3';56,
60:2'',3''][5,6]fullerene-C60-lh), graphene, or a metal oxide, like
for example, ZnO.sub.x, TiO.sub.x, ZTO, MoO.sub.x, NiO.sub.x, to
form the active layer in an OPV or OPD device.
[0144] The device preferably further comprises a first transparent
or semi-transparent electrode on a transparent or semi-transparent
substrate on one side of the active layer, and a second metallic or
semi-transparent electrode on the other side of the active
layer.
[0145] Further preferably the OPV or OPD device comprises, between
the active layer and the first or second electrode, one or more
additional buffer layers acting as hole transporting layer and/or
electron blocking layer, which comprise a material such as metal
oxide, like for example, ZTO, TiO.sub.x, MoO.sub.x, NiO.sub.x, a
conjugated polymer electrolyte, like for example PEDOT:PSS, a
conjugated polymer, like for example polytriarylamine (PTAA), an
organic compound, like for example
N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'diamine
(NPB),
N,N'-diphenyl-N,N'-(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine
(TPD).
[0146] In the blend or mixture of a p-type semiconducting polymer
and a fullerene or modified fullerene, the ratio polymer:fullerene
is preferably from 5:1 to 1:5 by weight, more preferably from 1:1
to 1:3 by weight, most preferably 1:1 to 1:2 by weight. A polymeric
binder may also be included, from 5 to 95% by weight. Examples of
binder include polystyrene(PS), polypropylene (PP) and
polymethylmethacrylate (PMMA).
[0147] To produce thin layers in BHJ OPV devices the compounds,
polymers, polymer blends or formulations of the present invention
may be deposited by any suitable method. Liquid coating of devices
is more desirable than vacuum deposition techniques. Solution
deposition methods are especially preferred. The formulations of
the present invention enable the use of a number of liquid coating
techniques. Preferred deposition techniques include, without
limitation, dip coating, spin coating, ink jet printing, nozzle
printing, letter-press printing, screen printing, gravure printing,
doctor blade coating, roller printing, reverse-roller printing,
offset lithography printing, dry offset lithography printing,
flexographic printing, web printing, spray coating, dip coating,
curtain coating, brush coating, slot dye coating or pad printing.
For the fabrication of OPV devices and modules area printing method
compatible with flexible substrates are preferred, for example slot
dye coating, spray coating and the like.
[0148] Suitable solutions or formulations containing the blend or
mixture of a p-type semiconducting polymer with a C.sub.60 or
C.sub.70 fullerene or modified fullerene like PCBM must be
prepared. In the preparation of formulations, suitable solvent must
be selected to ensure full dissolution of both component, p-type
and n-type and take into account the boundary conditions (for
example rheological properties) introduced by the chosen printing
method.
[0149] Organic solvents are generally used for this purpose.
Typical solvents can be aromatic solvents, halogenated solvents or
chlorinated solvents, including chlorinated aromatic solvents.
Examples include, but are not limited to chlorobenzene,
1,2-dichlorobenzene, chloroform, 1,2-dichloroethane,
dichloromethane, carbon tetrachloride, toluene, cyclohexanone,
ethylacetate, tetrahydrofuran, anisole, morpholine, o-xylene,
m-xylene, p-xylene, 1,4-dioxane, acetone, methylethylketone,
1,2-dichloroethane, 1,1,1-trichloroethane,
1,1,2,2-tetrachloroethane, ethyl acetate, n-butyl acetate,
dimethylformamide, dimethylacetamide, dimethylsulfoxide, tetraline,
decaline, indane, methyl benzoate, ethyl benzoate, mesitylene and
combinations thereof.
[0150] In the OPV devices of the present invent invention the
p-type and n-type semiconductor materials are preferably selected
from the materials, like the polymer/fullerene systems, as
described above
[0151] When the active layer is deposited on the substrate, it
forms a BHJ that phase separate at nanoscale level. For discussion
on nanoscale phase separation see Dennler et al, Proceedings of the
IEEE, 2005, 93 (8), 1429 or Hoppe et al, Adv. Func. Mater, 2004,
14(10), 1005. An optional annealing step may be then necessary to
optimize blend morpohology and consequently OPV device
performance.
[0152] Another method to optimize device performance is to prepare
formulations for the fabrication of OPV(BHJ) devices that may
include high boiling point additives to promote phase separation in
the right way. 1,8-octanedithiol, 1,8-diiodooctane, nitrobenzene,
chloronaphthalene, and other additives have been used to obtain
high-efficiency solar cells. Examples are disclosed in J. Peet, et
al, Nat. Mater., 2007, 6, 497 or Frechet et al. J. Am. Chem. Soc.,
2010, 132, 7595-7597.
[0153] Alternatively, the formulation according to the invention
can be used as ETL in OLEDs. Common OLEDs are realized using
multilayer structures. An emission layer is generally sandwiched
between one or more electron-transport and/or hole-transport
layers. By applying an electric voltage electrons and holes as
charge carriers move towards the emission layer where their
recombination leads to the excitation and hence luminescence of the
lumophor units contained in the emission layer. The formulations
according to the present invention may be employed in one or more
of the electron transport layers, The selection, characterization
as well as the processing of the other layers and of the materials
used therein is generally known by a person skilled in the art,
see, e.g., Muller et al, Synth. Metals, 2000, 111-112, 31-34,
Alcala, J. Appl. Phys., 2000, 88, 7124-7128 and the literature
cited therein.
[0154] Unless the context clearly indicates otherwise, as used
herein plural forms of the terms herein are to be construed as
including the singular form and vice versa.
[0155] Throughout the description and claims of this specification,
the words "comprise" and "contain" and variations of the words, for
example "comprising" and "comprises", mean "including but not
limited to", and are not intended to (and do not) exclude other
components.
[0156] Above and below, unless stated otherwise percentages are
percent by weight and temperatures are given in degrees Celsius.
The values of the dielectric constant E ("permittivity") refer to
values taken at 20.degree. C. and 1,000 Hz. Room temperature,
unless stated otherwise, means 20.degree. C.
[0157] It will be appreciated that variations to the foregoing
embodiments of the invention can be made while still falling within
the scope of the invention. Each feature disclosed in this
specification, unless stated otherwise, may be replaced by
alternative features serving the same, equivalent or similar
purpose. Thus, unless stated otherwise, each feature disclosed is
one example only of a generic series of equivalent or similar
features.
[0158] All of the features disclosed in this specification may be
combined in any combination, except combinations where at least
some of such features and/or steps are mutually exclusive. In
particular, the preferred features of the invention are applicable
to all aspects of the invention and may be used in any combination.
Likewise, features described in non-essential combinations may be
used separately (not in combination).
[0159] The invention will now be described in more detail by
reference to the following examples, which are illustrative only
and do not limit the scope of the invention.
EXAMPLES
Examples Labelled "C" are Comparison Examples
[0160] OPV devices having the following layer sequence were
prepared as described below: Glass substrate/ITO
electrode/HTL/BHJ/ETL/Al electrode
[0161] ITO patterned glass substrates are cleaned using ultra-sonic
bath of successively: 3 min in acetone, 3 min in IPA, 3 min in
deionized water. The HTL made of PEDOT:PSS is then deposited by
spin-coating in air. The film is annealed at 130 C during 30 min
under N.sub.2. A volume of 80 .mu.L of the solution of BHJ is
coated under N.sub.2 using Doctor-Blade technique at a blade speed
of 40 mm/s, with a screw gap of 60 .mu.m, and maintaining the plate
temperature at 70 C. It is then dried 2 min at 70 C in N.sub.2. A
volume of 30 .mu.L of the ETL formulations are coated in air using
a Doctor-Blade technique at a blade speed of 20 mm/s, with a screw
gap of 40 .mu.m, and maintaining the plate temperature at Room
Temperature. Devices are then completed by a thermal evaporation of
Aluminium in a special chamber having a pressure of 10.sup.-6
mbar.
[0162] The photoactive layer with the BHJ comprises a blend of one
of the conjugated polymers P1, P2, P3 and P4 as shown below,
respectively, with the fullerene C.sub.60-PCBM
##STR00006##
[0163] Mn=27000 g/mol, Mw=65700 g/mol, PDI=2.41
##STR00007##
[0164] Mw=41200 g/mol, Mn=22100 g/mol, PDI=1.86
##STR00008##
[0165] Mw=60068 g/mol, Mn=39577 g/mol, PDI=1.52
[0166] P4: Poly(3-hexylthiophene), Mw=77500 g/mol, Mn=38700
g/mol
[0167] The ETL comprises a layer of a formulation comprising one of
the salts S1, S2 and S3 or one of the ionic liquids IL1 to IL8 as
shown below. Control devices were prepared having the same layer
structure but without an ETL.
##STR00009## ##STR00010##
Examples 1-6
[0168] The average parameters of the devices having the
architecture {Glass/ITO/BHJ(Lisicon OPV polymer P1:PCBM)/ETL/Al}
and using ETLs based on salt S1, S2 or S3, or without an ETL, are
summarized in Table 1.
TABLE-US-00001 TABLE 1 ETL/cathode Conc. V.sub.OC J.sub.SC FF PCE
PCE Max. Ex. Salt (mg/ml) (H.sub.2O:IPA) (mV) (mA cm.sup.2) (%) (%)
SD (%) n.sub.ave/max PCE (%) 1C Al only 743 -10.91 69.4 5.63 0.11
0.98 5.77 2 S1 0.6 4:1 806 -11.01 74.5 6.60 0.18 0.97 6.80 3C Al
only 751 -11.10 70.2 5.85 0.10 0.97 6.02 4 S2 0.6 4:1 800 -11.06
73.6 6.51 0.22 0.94 6.94 5C Al only 751 -11.10 70.2 5.85 0.10 0.97
6.02 6 S3 0.6 1:4 770 -11.42 71.3 6.27 0.24 0.96 6.54
[0169] Compared to the OPV devices of Examples 2, 4 and 6 in
accordance with the invention, which comprise an ETL made from a
formulation based on salt S1, S2 or S3, respectively, the reference
devices of comparison examples 1C, 3C and 5C, without ETL, show
lower performance.
Examples 7-9
[0170] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Al} and using an
ETL based on salt S3 (Ex. 9), or without an ETL (Ex. 7C) or just
washed by the solvent (Ex. 8C), are summarized in Table 2.
TABLE-US-00002 TABLE 2 ETL/cathode Conc. V.sub.OC J.sub.SC FF PCE
PCE Max. Ex. Salt (mg/ml) (H.sub.2O:IPA) (mV) (mA cm.sup.2) (%) (%)
SD (%) n.sub.ave/max PCE (%) 7C Al only 686 -10.43 67.2 4.81 0.31
0.95 5.08 8C Al only (BHJ is washed 647 -9.34 65.8 3.98 0.37 0.91
4.37 with the solvent used for depositing the formulation) 9 S3
1.25 4:1 800 -10.74 72.6 6.24 0.33 0.95 6.59
[0171] Compared to the OPV device of Example 9 in accordance with
the invention, which comprises an ETL made from a formulation based
on salt S3, the reference devices of comparison examples 7C without
ETL, or of Example 8C without ETL and wherein the BHJ is washed by
the solvent used for depositing the formulation with S3 in Example
9, show lower performance.
Examples 10-15
[0172] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Al} and using ETLs
based on salt 1 and different combinations of water and
isopropanol, or without an ETL (Ex.10C), are summarized in Table
3.
TABLE-US-00003 TABLE 3 ETL/cathode Conc. of S3 V.sub.OC J.sub.SC FF
PCE PCE Max. Ex. (mg/ml) (H.sub.2O:IPA) (mV) (mA cm.sup.2) (%) (%)
SD (%) n.sub.ave/max PCE (%) 10C Al only 729 -6.22 65.6 2.97 0.15
0.93 3.19 11 1.25 4:1 793 -8.84 66.9 4.68 0.40 0.91 5.15 12 1.25
2:1 787 -9.00 69.2 4.90 0.33 0.94 5.19 13 1.25 1:1 750 -8.86 54.6
3.62 0.56 0.90 4.02 14 1.25 1:2 784 -8.96 66.7 4.69 0.42 0.92 5.08
15 1.25 1:4 740 -8.06 64.8 3.87 0.59 0.83 4.64
[0173] Compared to the OPV devices of Examples 11-15 in accordance
with the invention, which comprise an ETL made from a formulation
based on salt S3 and various solvent combinations of water and
isopropanol, respectively, the reference device of comparison
examples 10C without ETL shows lower performance.
Examples 16-22
[0174] The average parameters of devices having the architecture
{Glass/ITO/BHJ (Lisicon OPV Polymer P1:PCBM)/ETL/Al} and using ETLs
based on salt 1 in different concentrations, or without an ETL
(Ex.16), are summarized in Table 4.
TABLE-US-00004 TABLE 4 ETL/cathode Conc. of S3 V.sub.OC J.sub.SC FF
PCE PCE Max. Ex. (mg/ml) (H.sub.2O:IPA) (mV) (mA cm.sup.2) (%) (%)
SD (%) n.sub.ave/max PCE (%) 16C Al only 686 -10.43 67.2 4.81 0.31
0.95 5.08 17 1.25 4:1 800 -10.74 72.6 6.24 0.33 0.95 6.59 18 2.5
4:1 794 -10.54 71.4 5.98 0.50 0.93 6.44 19 5.0 4:1 793 -10.61 67.8
5.71 0.57 0.91 6.24 20C Al only 735 -10.44 65.5 5.03 0.24 0.97 5.19
21 1.25 4:1 812 -10.67 73.3 6.34 0.14 0.97 6.56 22 0.6 4:1 808
-10.46 73.7 6.24 0.40 0.93 6.71
[0175] Compared to the OPV devices of Examples 17-19 and 21-22 in
accordance with the invention, which comprise an ETL made from a
formulation based on salt S3 in various concentrations,
respectively, the reference devices of comparison examples 16C and
20C, without ETL, show lower performance.
Examples 23-25
[0176] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Al} and using ETLs
based on salt S1 (Ex. 25) or calcium (Ex.23C), or without an ETL
(Ex.24C), are summarized in Table 5.
TABLE-US-00005 TABLE 5 V.sub.OC J.sub.SC FF PCE PCE Max. Ex.
ETL/cathode (mV) (mA cm.sup.2) (%) (%) SD (%) n.sub.ave/max PCE(%)
23C Ca/Al 807 -9.92 76.0 6.08 0.36 0.95 6.42 24C Al only 735 -10.44
65.5 5.03 0.24 0.97 5.19 25 S3/Al 812 -10.67 73.3 6.34 0.14 0.97
6.56
[0177] Compared to the OPV devices of Example 25 in accordance with
the invention, which comprises an ETL made from a formulation based
on salt S1, the reference devices of comparison examples 23C and
24C, with a calcium ETL or without ETL, respectively show lower
performance.
Examples 26-33
[0178] The average parameters of devices having the architecture
{Glass/ITO/BHJ/ETL/Al} and using ETLs based on salt 1 and different
electron-donating polymers in the BHJs are summarized in Table
6.
TABLE-US-00006 TABLE 6 V.sub.OC J.sub.SC FF PCE PCE Max. Ex. BHJ
ETL/cathode (mV) (mA cm.sup.2) (%) (%) SD (%) n.sub.ave/max PCE (%)
26C P1:PCBM Al only 721 -10.42 64.2 4.82 0.19 0.95 5.09 27 P1:PCBM
S1/Al 807 -10.82 71.3 6.22 0.30 0.93 6.68 28C P4:PCBM Al only 327
-5.41 51.8 0.92 0.05 0.94 0.98 29 P4:PCBM S1/Al 481 -5.54 54.4 1.45
0.25 0.77 1.89 30C P2:PCBM Al only 621 -7.92 42.7 2.11 0.32 0.90
2.33 31 P2:PCBM S1/Al 619 -8.35 43.4 2.25 0.17 0.91 2.46 32C
P3:PCBM Al only 803 -6.51 38.0 1.99 0.06 0.94 2.11 33 P3:PCBM S1/Al
948 -6.97 43.2 2.85 0.11 0.95 3.01
[0179] Compared to the OPV devices of Examples 27, 29, 31 and 33 in
accordance with the invention, which comprise an ETL made from a
formulation based on salt S1, respectively, the reference devices
of comparison examples 28C, 30C and 32C, without ETL, show lower
performance, even if the composition of the BHJ is changed.
Examples 34-35
[0180] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Al} and using an
ETL obtained from a formulation comprising 0.5 vol % ionic liquid
IL1 and 99.5 vol % methanol (Ex. 35), or without an ETL (Ex. 34C),
are summarized in Table 7.
TABLE-US-00007 TABLE 7 ETL/cathode IL Speed V.sub.OC J.sub.SC FF
PCE PCE Max. Ex. Type (rpm) (vol % IL) (mV) (mA cm.sup.2) (%) (%)
SD (%) n.sub.ave/max PCE (%) 34C Al only 729 -13.60 64.2 6.36 0.31
0.91 6.95 35 IL1 2000 0.5 752 -13.53 65.7 6.68 0.22 0.94 7.08
[0181] Compared to the OPV device of Example 35 in accordance with
the invention, which comprises an ETL made from a formulation based
on ionic liquid IL1 and methanol, the reference device of
comparison example 34C without ETL shows lower performance.
Examples 36-37
[0182] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Al} and using an
ETL obtained from a formulation comprising 0.018 vol % ionic liquid
IL1 and 99.982 vol % isopropanol (Ex. 37), or without an ETL (Ex.
36C), are summarized in Table 8.
TABLE-US-00008 TABLE 8 ETL/cathode V.sub.OC J.sub.SC FF PCE PCE
Max. Ex. IL Type (vol % IL) (mV) (mA cm.sup.2) (%) (%) SD (%)
n.sub.ave/max PCE (%) 36C Al only 736 -11.41 68.9 5.79 0.58 0.84
6.35 37 IL1 0.018 795 -12.10 72.1 6.93 0.23 0.95 7.26
[0183] Compared to the OPV device of Example 37 in accordance with
the invention, which comprises an ETL made from a formulation based
on ionic liquid IL1 and isopropanol, the reference device of
comparison example 36C without ETL shows lower performance.
Examples 38-41
[0184] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Al} and using an
ETL obtained from a formulation comprising ionic liquid IL1 and
isopropanol in different volumic ratios (Ex. 39-41), or without an
ETL (Ex. 38C), are summarized in Table 9.
TABLE-US-00009 TABLE 9 ETL/cathode V.sub.OC J.sub.SC FF PCE PCE
Max. Ex. IL Type (vol % IL) (mV) (mA cm.sup.2) (%) (%) SD (%)
n.sub.ave/max PCE (%) 38C Al only 736 -11.41 68.9 5.79 0.58 0.84
6.35 39 IL1 0.036 793 -11.38 69.8 6.30 0.15 0.96 6.55 40 IL1 0.018
795 -12.10 72.1 6.93 0.23 0.95 7.26 41 IL1 0.0036 800 -12.18 71.4
6.96 0.18 0.97 7.20
[0185] Compared to the OPV devices of Examples 39-41 in accordance
with the invention, which comprises an ETL made from a formulation
based on ionic liquid IL1 and isopropanol in different ratios, the
reference device of comparison example 38C without ETL shows lower
performance. Table 9 also shows that the varying the concentration
of the IL in the solvent the performance can be optimised.
Examples 42-44
[0186] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Al} and using an
ETL obtained from a formulation comprising 0.18 vol % ionic liquid
IL1 and 99.82 vol % of either isopropanol or methanol (Ex. 43-44),
or without an ETL (Ex. 42C), are summarized in Table 10.
TABLE-US-00010 TABLE 10 ETL/cathode IL V.sub.OC J.sub.SC FF PCE PCE
Max. Ex. Type (vol % IL) (mV) (mA cm.sup.2) (%) (%) SD (%)
n.sub.ave/max PCE (%) 42C Al only 736 -11.41 68.9 5.79 0.58 0.84
6.35 43 IL1 0.18 738 -11.19 52.5 4.34 0.56 0.83 5.23 methanol 44
IL1 0.18 773 -11.97 69.1 6.39 0.26 0.95 6.74 isopropanol
[0187] The OPV device of Example 44 in accordance with the
invention, which comprises an ETL made from a formulation based on
ionic liquid IL1 and isopropanol shows better performance than the
reference device of comparison example 42C without ETL.
[0188] On the other hand, the OPV device of Example 43 in
accordance with the invention, which comprises an ETL made from a
formulation based on ionic liquid IL1 and methanol shows lower
performance, and also lower performance than the device of example
35 with a higher ratio of IL1 in methanol. This shows that by
varying the concentration of the IL in the solvent the performance
can be optimised.
Examples 45-46
[0189] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Ag/Al} and using
ETLs based on salt S1 (Ex. 46) or without an ETL (Ex.45C), are
summarized in Table 11.
TABLE-US-00011 TABLE 11 V.sub.OC J.sub.SC FF PCE Max. Ex.
ETL/cathode (mV) (mA cm.sup.2) (%) (%) PCE (%) 45C Ag/Al 754 12.48
67.6 6.36 6.96 46 S1 800 14.58 70.8 8.27 9.09
[0190] Compared to the OPV devices of Example 46C in accordance
with the invention, which comprise an ETL made from a formulation
based on salt S1, S2 or S3, respectively, the reference devices of
comparison example 45 without ETL, show lower performance.
Examples 47-56
[0191] The average parameters of devices having the architecture
{Glass/ITO/BHJ(Lisicon OPV Polymer P1:PCBM)/ETL/Ag/Al} and using
ETLs based on ionic liquid IL2, or ionic liquid IL3, or ionic
liquid IL3, or ionic liquid IL4, or ionic liquid IL5, or ionic
liquid IL6, or ionic liquid IL7, or ionic liquid IL8 or without an
ETL (Ex.47C), are summarized in Table 12.
TABLE-US-00012 TABLE 12 ETL/ V.sub.oc J.sub.sc FF PCE Ex. cathode
(mV) (mA cm.sup.2) (%) (%) 47C Ag/Al 754 12.48 67.6 6.36 48 IL2 797
13.4 71.2 7.62 49 IL3 774 13.6 68.6 7.21 50 IL4 790 13.3 71.2 7.50
51 IL5 801 12.66 70.1 7.11 52 IL6 801 13.1 70.2 7.38 53 IL7 801
12.9 71.6 7.39 54 IL8 798 13.9 67.6 7.49
[0192] Compared to the OPV devices of Examples 48, 49, 50, 51, 52,
53, 54 in accordance with the invention, which comprise an ETL made
from a formulation based on an ionic liquid as IL2, or IL3, or IL4,
or IL5, or IL6, or IL7, or IL8, respectively, the reference devices
of comparison example 47C without ETL, show lower performance.
* * * * *
References